1. Field of the Invention
This invention relates in general to perpendicular recording, and more particularly to a method and apparatus for providing a truncated write head probe for perpendicular recording using a pullback of a resist.
2. Description of Related Art
Fixed magnetic storage systems are now commonplace as a main non-volatile storage in modem personal computers, workstations, and portable computers. Storage systems are now capable of storing gigabyte quantities of digital data, even when implemented in portable computers.
Many important advances have been made that provide higher data density and thus increased storage capacities for storage systems. These advances include faster access speeds and faster access times resulting in a greater bandwidth of data communicated to and from the storage systems. Advances have also been made by greatly reducing the size and weight of the storage systems, resulting in the availability of ultra-light portable computers having state-of-the art capabilities and performance.
A disk drive is one example of a storage system. Disk drive magnetic recording densities have increased tremendously in the past few years - faster than any other means of information storage. Thus far, all production disk drives have used longitudinal recording medium. In longitudinal recording, a disk drive's recording head senses the magnetic transitions in the magnetic media that coats the disk as the head flies over the rapidly rotating disk. The amplitude of this signal is proportional to the media's magnetic thickness; a product of the media's remanent magnetic moment density (“Mr”) and its physical thickness (“t”). As data densities increase, the media's magnetic thickness (known technically as Mrt) must be decreased proportionately so the closely packed transitions will be sharp enough to be read clearly. For conventional media, this means a decrease in the physical thickness of the media.
The success of longitudinal magnetic recording is rapidly approaching its limit. The point at which a magnetic domain transitions (i.e., the magnetic poles in a magnetic material change orientation or flip) under thermal fluctuations (superparamagnetic limit) will ultimately be the limit to scaling down any magnetic domain. The superparamagnetic effect originates from the shrinking volume of magnetic grains that compose the hard-disk media, in which data bits are stored as alternating magnetic orientations. Designers have shrunk the media's grain diameters and decreased the thickness of the media to increase data-storage densities while maintaining acceptable performance. However, the resulting smaller grain volume makes the magnetic grain increasingly susceptible to thermal fluctuations, which decreases the signal sensed by the drive's read/write head. If the signal reduction is great enough, data could be lost in time due to this superparamagnetic effect.
Hence, it has been long known that longitudinal recording is not the ideal recording method for maximizing magnetic areal densities. It has been predicted, and it is widely accepted, that the practical limit of longitudinal recording will be around 80-200 GB/in2.
One obvious solution is to change the number of grains per bit in a magnetic material (bit cell) to extend the superparamagnetic limit. However, present manufacturing of longitudinal recording media is directed towards producing a thinner media in order to achieve better linear resolution as discussed above.
An alternative to longitudinal recording is perpendicular recording in which the medium is magnetized perpendicular to the surface of the disk. In a perpendicular recording medium, the volume per magnetic grain can be larger than in a longitudinal recording medium. However, when perpendicular recording is used with a longitudinal recording medium, as the medium's magnetic thickness (Mrt) and corresponding thickness of the magnetic write head pole tips are reduced, the write sensitivity decreases.
One known solution to avoid such an event is to introduce a soft magnetic layer under a thicker perpendicular recording medium; the soft magnetic under layer (SUL) having a high saturation magnetization (Ms) and high coercive field (He). Moreover, the perpendicular medium provides better thermal stability and a larger bit cell by permitting a thicker recording layer. Accordingly, the soft magnetic under layer introduced to the medium allows perpendicular recording to provide very high recording densities. However, in order to realize the very high recording densities, a width of a write head probe, which is limited by the pole thickness, must be reduced. In addition, a write head must provide a pole flux density near a saturation flux density of the write head material to generate a flux density greater than the residual flux density of the magnetic material.
It can also be seen that there is a need for a magnetic write head having a writing probe with a narrower profile to achieve a very high recording density at very high data rates.
It can be seen that there is a need for a magnetic write head to have a pole flux density near a saturation flux density of the magnetic write head material.